Shaft assembly with internal uv-cured balance weight

ABSTRACT

A method for forming a shaft assembly includes: providing a shaft structure, the shaft structure comprising a shaft and a universal joint member that is coupled to an end of the shaft; inserting a weight member to the shaft structure to form an intermediate assembly, the weight member being formed at least partly from a liquid resin, the intermediate assembly having an initial rotational unbalance; rotating the intermediate assembly about a longitudinal axis of the shaft structure to re-distribute a least a portion of the weight member circumferentially about the shaft structure to at least partly attenuate the initial rotational unbalance; and curing the liquid resin while rotating the intermediate assembly to fix the re-distributed portion of the weight member to the shaft structure to thereby form a balance weight that at least partly attenuates the initial rotational unbalance. A shaft assembly is also provided.

FIELD

The present disclosure relates to shaft assembly with an internalbalance weight and a related method for forming the shaft assembly.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Various shafts assemblies, such as propshafts used in the automotiveindustry to transmit rotary power from a powertrain to an axle ortransfer case, must be rotationally balanced so that undesired vibrationis not generated during the use of the shaft assembly. In the productionof modern automotive propshafts, it is common practice to weld anappropriately sized balance weight to a portion of the propshaft tominimize unbalance. This solution, however, is known to suffer fromseveral drawbacks.

For example, it is desirable to form automotive propshafts fromincreasingly thinner-walled tubing in an effort to reduce the cost andmass of the propshaft. The welding of balance weights to suchthin-walled tubing, however, requires more precise control of thewelding operation and moreover, may create stress-risers in the tubing.

Accordingly, there remains a need in the art for an improvedrotationally balanced shaft assembly and for an improved method forforming a rotationally balanced shaft assembly.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

In one form, the present teachings provide a method for forming a shaftassembly. The method includes: providing a shaft structure, the shaftstructure comprising a shaft and a universal joint member that iscoupled to an end of the shaft; inserting a weight member to the shaftstructure to form an intermediate assembly, the weight member beingformed at least partly from a liquid resin, the intermediate assemblyhaving an initial rotational unbalance; rotating the intermediateassembly about a longitudinal axis of the shaft structure tore-distribute a least a portion of the weight member circumferentiallyabout the shaft structure to at least partly attenuate the initialrotational unbalance; and curing the liquid resin while rotating theintermediate assembly to fix the re-distributed portion of the weightmember to the shaft structure to thereby form a balance weight that atleast partly attenuates the initial rotational unbalance.

In another form, the present teachings provide a shaft assembly thatincludes a shaft structure and a balance weight. The shaft structure hasa shaft and a universal joint member coupled to an end of the shaft anddefines a hollow interior zone. The balance weight is received in thehollow interior zone and is fixedly coupled to the shaft structure. Thebalance weight is at least partly formed of a cured resin and isnon-uniformly distributed in a circumferential direction about alongitudinal axis of the shaft structure. The balance weight isconfigured to reduce a rotational unbalance of the shaft structure abouta longitudinal axis of the shaft structure.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a side elevation view in partial section of an exemplary shaftassembly constructed in accordance with the teachings of the presentdisclosure;

FIG. 2 is perspective view of a portion of the shaft assembly of FIG. 1illustrating a balance weight mounted in a universal joint member;

FIG. 3 is a longitudinal section view of a portion of a shaft assemblydepicting a nozzle for injecting a liquid resin material into a shaftstructure;

FIG. 4 is a view similar to that of FIG. 3 but depicting a light sourcereceived into the shaft structure to cure the liquid resin material;

FIG. 5 is a view similar to that of FIG. 3 but depicting an alternateembodiment in which a cartridge is assembled to the shaft structure, thecartridge including a housing that holds a liquid resin; and

FIG. 6 is a perspective view of a portion of the alternate embodiment ofFIG. 5 illustrating a balance weight mounted in a universal jointmember.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

With reference to FIG. 1 of the drawings, an exemplary shaft assemblyconstructed in accordance with the teachings of the present disclosureis generally indicated by reference numeral 10. The shaft assembly 10can be any type of shaft assembly that is configured to transmit rotarypower, but in the particular example provided, the shaft assembly 10 isa propshaft that is employed in a vehicle driveline to transmitpropulsive rotary power.

The shaft assembly 10 can include a shaft member 12, first and seconduniversal joints 14 and 16, respectively, and one or more balanceweights 18. Only one balance weight 18 is shown in the example provided,but it will be appreciated that one or more of the balance weights 18can be employed where unbalance correction is desired, such as at theopposite ends of the shaft assembly 10. Except as noted herein, theshaft member 12 and the first and second universal joints 14 and 16 canbe constructed in a conventional manner and as such, a detaileddiscussion of these components is not needed herein. Briefly, the shaftmember 12 can be a tubular structure that can be formed of anappropriate material, such as steel, aluminum, carbon fiber, etc. Thefirst and second universal joints 14 and 16 can be configured to permitrelative movement between the driveline components while transmittingrotary power. For example, the first and second universal joints 14 and16 can be Cardan joints, or can be a type of constant velocity joint.Each of the first and second universal joints 14 and 16 can include auniversal joint member 20 that can be fixedly coupled to the shaftmember 12 to form a shaft structure 24.

In the particular example provided, each of the first and seconduniversal joints 14 and 16 is a Cardan joint, and the universal jointmembers 20 are yokes that are fixedly coupled (e.g., via welding) to theshaft member 12 to form the shaft structure 24. Each of the yokes cancomprise a pair of arms 30 having a hole 32 formed there through. Theholes 32 in the arms 30 are conventionally configured to receive bearingassemblies 36 therein that support the trunnions 38 of a cross-shaft 40.

With reference to FIGS. 1 and 2, the balance weight 18 can be receivedinto a hollow interior zone 42 in the assembly 10 and can be fixedlycoupled to the shaft structure 24 for rotation therewith. The hollowinterior zone 42 could be disposed entirely within the hollow interiorof the shaft member 12, could be disposed entirely within an associatedone of the universal joint members 20, or could be disposed within boththe shaft member 12 and one or both of the universal joint members 20.

The balance weight 18 can be at least partially formed of a cured resin44 and can optionally comprise particles 46 that are formed of amaterial having a density that is greater than a density of the curedresin 44. In the example provided, the balance weight 18 includes steelparticles 46 that are spherically shaped and have a density that isapproximately 6 to 8 times that of the cured resin 44. It will beappreciated, however, that the particles 46 could be formed of one ormore different materials, and/or could be formed of two or more sizes,and/or could be formed of one or more shapes, and/or that one or more ofthe shape could be a non-spherical shape. The balance weight 18 can benon-uniformly distributed in a circumferential direction about alongitudinal axis 50 of the shaft structure 24 so as to reduce arotational unbalance of the shaft structure 24 about its longitudinalaxis 50.

The material that forms the balance weight 18 can be installed to thehollow interior zone 42 prior to or after one or both of the universaljoint members 20 have been fixedly coupled to the shaft member 12. Forexample, material (i.e., a liquid comprising an uncured resin 44 withthe optional higher-density particles 46 mixed therein) can be injectedinto the hollow interior zone 42. The shaft structure 24, with orwithout the entirety of the first universal joint 14 (FIG. 1) and/or thesecond universal joint 16 (FIG. 1), can be rotated about itslongitudinal axis 50 at a speed that is within a predeterminedrotational speed range to re-distribute the material, and there-distributed material can be cured while the shaft structure 24 isbeing rotated to thereby form the balance weight 18. It will beappreciated that rotation of the shaft structure 24 while the uncuredresin is in a liquid state will permit portions of the material,including the higher density particles 46 if employed, to re-distributein a circumferential direction in a manner that reduces the rotationalunbalance of the shaft structure 24 about its longitudinal axis 50.Accordingly, curing the liquid resin 44 after re-distribution of thematerial in the circumferential direction locks the material (i.e., theresin and if included, the higher density particles 46) into anorientation relative to the shaft structure 24 that maintains thereduced rotational unbalance that was obtained prior to the curing ofthe liquid resin 44.

To expedite curing of the liquid resin 44, ultra-violet (UV) light maybe employed. UV light could be introduced to the hollow interior zonethrough any convenient means, such as through a hole 60 formed through auniversal joint member 20 that is disposed along the longitudinal axis50 of the shaft structure 24. The hole 60 could also be employed tointroduce the material to the hollow interior zone 42. With reference toFIG. 3, a nozzle 70 can be inserted through the hole 60 and the materialcan be pumped through the nozzle 70 to introduce the material to thehollow interior zone 42. Thereafter, and once the material has beenre-distributed, a UV light source 72 (FIG. 4) can be translated throughthe hole 60 into the hollow interior zone 42 so that UV light from theUV light source 72 (FIG. 4) can expedite the curing of the liquid resin44 in the material.

With reference to FIGS. 5 and 6, a filament 80 that is formed of amaterial that is capable of transmitting UV light there through, such asa fiber-optic material, can be employed to facilitate the transmissionof UV light into the hollow interior zone 42. The filament 80 can have arelatively small diameter, thread-like structure that can receive UVlight from a UV light source 84 that is located outside the shaftstructure 24 and transmit the UV light to the liquid resin 44 in thehollow interior zone 42 to facilitate expedited curing of the liquidresin 44. Optionally, a lens 90 can be coupled to the universal jointmember 20 and can collect the UV light and transmit the UV light to thefilament 80. In the example provided, the lens 90 is received in thehole 60 and is fixedly coupled to both the universal joint member 20 andthe filament 80.

If desired, the material M (i.e., the liquid resin 44 and the higherdensity particles 46, if any) can be disposed in a cartridge C that canbe assembled to the universal joint member 20 or the shaft member 12(FIG. 1) prior to the coupling of the universal joint member 20 to theshaft member 12 (FIG. 1). For example, the cartridge C can include ahousing H, which can be shaped as a hollow ring torus or an annular orcylindrical plinth, and the material M (i.e., the liquid resin 44 withthe heavier density particles 46 if included), can be received into thehousing H. The housing H can be formed of a material that permits UVlight to be transmitted there through, such as a transparent plasticmaterial, and can be secured to the shaft member 12 and/or the universaljoint member 20 in any desired manner, such as via a press-fittingand/or adhesive bonding. If a filament 80 is to be employed, thefilament 80 could be optionally fixedly coupled to the housing H.

The above method and balance weight permit the shaft assembly 10 to berotationally balanced without affecting the exterior surface of theshaft assembly 10. Accordingly, it would be possible to rotationallybalance the shaft assembly 10 after the shaft assembly 10 has beencoated with a substance, such as paint, that would otherwise interferewith the welding of a balance weight to an exterior surface of the shaftassembly 10. Moreover, in the event that the above method is notsuccessful in entirely reducing the rotational unbalance of the shaftstructure within predetermined limits, another rotational balancingmethod, such as the welding of balance weights to an exterior surface ofthe shaft structure 24, could be employed.

While the method for forming the shaft assembly 10 has been described asemploying physical forces attendant to the rotation of the shaftstructure 24 about its longitudinal axis 50, it will be appreciated thata magnetic field or other means could be employed to move the higherdensity particles about the circumference of the shaft structure 24 toattenuate the initial rotational unbalance of the shaft structure 24. Ifa magnetic field is employed in addition to the physical forcesattendant to the rotation of the shaft structure 24, the magnetic fieldwould need to be tailored to the unbalance in its shape, magnitude andorientation relative to the shaft structure 24.

Moreover, while the above method and balance weight 18 have beendescribed as being received into a hollow interior zone of the shaftassembly 10, it will be appreciated that the balance weight 18 (and moreparticularly the embodiment of the balance weight 18 that includes thehousing—) can be fixedly mounted to an exterior surface of the shaftstructure 24 so that it is not necessary to transmit UV light into theinterior of the shaft structure 24.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A shaft assembly having a hollow interior zone,the shaft assembly comprising: a shaft structure having a shaft and auniversal joint member coupled to an end of the shaft; and a balanceweight received in the hollow interior zone and fixedly coupled to theshaft structure, the balance weight being at least partly formed of acured resin, the balance weight being non-uniformly distributed in acircumferential direction about a longitudinal axis of the shaftstructure, the balance weight being configured to reduce a rotationalunbalance of the shaft structure about a longitudinal axis of the shaftstructure.
 2. The shaft assembly of claim 1, wherein the balance weightcomprises particles formed of a material having a density that isgreater than a density of the cured resin.
 3. The shaft assembly ofclaim 2, wherein the particles are formed of steel.
 4. The shaftassembly of claim 1, wherein the balance weight comprises a filamentthat is received in the hollow interior zone in the shaft assembly, thefilament being formed of a material that is configured to transmit UVlight there through.
 5. The shaft assembly of claim 4, wherein thefilament extends into a hole that is formed through the universal jointmember.
 6. The shaft assembly of claim 5, wherein the hole is formedalong the longitudinal axis.
 7. The shaft assembly of claim 1, whereinthe universal joint member comprises a pair of arms, each of the armshaving a hole formed there through.
 8. A method for forming a shaftassembly, the method comprising: providing a shaft structure, the shaftstructure comprising a shaft and a universal joint member that iscoupled to an end of the shaft; inserting a weight member to the shaftstructure to form an intermediate assembly, the weight member beingformed at least partly from a liquid resin, the intermediate assemblyhaving an initial rotational unbalance; rotating the intermediateassembly about a longitudinal axis of the shaft structure tore-distribute a least a portion of the weight member circumferentiallyabout the shaft structure to at least partly attenuate the initialrotational unbalance; and curing the liquid resin while rotating theintermediate assembly to fix the re-distributed portion of the weightmember to the shaft structure to thereby form a balance weight that atleast partly attenuates the initial rotational unbalance.
 9. The methodof claim 8, wherein curing the re-distributed portion of the weightmember comprises transmitting ultra-violet light into the shaftstructure.
 10. The method of claim 9, wherein a filament is receivedthrough the shaft structure and wherein the ultra-violet light istransmitted into the shaft structure through the filament.
 11. Themethod of claim 10, wherein the filament is disposed axially along thelongitudinal axis of the shaft structure and through the universal jointmember.
 12. The method of claim 8, wherein the weight member comprisesparticles formed of a material having a density that is greater than adensity of the liquid resin.
 13. The method of claim 12, wherein theparticles are formed of steel.